We have investigated the phenomenon of readsorption after pulsed-laser
induced thermal desorption during the presence of ambient gas. The te
mporal evolution of the readsorption of water has been measured as a f
unction of the ambient gas pressure for helium and carbon-dioxide atmo
spheres. CO2 pressures above 10 mbar lead to a virtually complete read
sorption of the desorbed material. A model based on a nearly one-dimen
sional diffusion scheme explains this remarkable result.